# K1321 — bounded channel messages

This snapshot extends the shared-object lifetime source with a fixed-size
channel queue. Isolated K1325 Image builds copy `handles.rs` into the kernel
runtime; the frozen root kernel source and earlier snapshots stay unchanged.

One `BoundedChannel` owns a kernel-minted nonzero Channel name, a shared handle
registry, and a ring with `DEPTH` message slots of at most `MAX` bytes each.
The creator receives read/write rights and may grant read or write subsets to
a second live process generation. A send requires write rights; a receive
requires read rights. Foreign, closed, stale-generation or wrong-kind handles
cannot access the queue. Messages are copied into kernel-owned slots, preserve
FIFO order and may be empty. A message of exactly `MAX` bytes is allowed.

Sending more than `MAX` bytes returns `MessageTooLarge` (EMSGSIZE 90). Sending
when all `DEPTH` slots are occupied returns `WouldBlock` (EAGAIN 11). An
empty receive returns `None` without changing state. The adapter must copy
user data into a private scratch buffer before a slot is published. If that
copy fails partway, it returns `Fault` (EFAULT 14), and the complete queue and
handle snapshot remains unchanged. Invalid owner, rights, capacity and length
checks likewise run before mutation. A successful receive consumes exactly
one slot. A read-only `peek` allows a kernel adapter to check and copy the
front message into user memory before committing the receive; a failed user
destination copy therefore leaves the message queued. Last close releases
every queued payload and resets ring indices;
earlier closes leave the queue intact while a reference remains.

K1321–K1324 require host positive and boundary tests, wrong-owner and
rights-denial tests, a partial-copy fault test, an AArch64 `no_std` metadata
build, and a mutant that publishes the partial copy and is rejected by the
fault test. K1325 requires native EL0 six-profile execution with one
byte-identical experimental Image. This model does not claim a blocking
scheduler wake or a production release gate.